The percentage of cTfr cells among CD4+ T cells appeared to be lower in PD patients than in HCs, but the difference was without statistically significant[1.05% (0.62–1.54%) 95%CI (0.79, 1.30%) vs. 1.3% (0.63–1.90%), 95%CI (0.72, 1.70%), P = 0.366, Figure 2C]. Here, CD4 is linked to Parkinson disease.